Effects of sulphurization time on Cu2ZnSnS4 absorbers and thin films solar cells obtained from metallic precursors

Abstract

We report the results of a study of the sulphurization time effects on Cu2ZnSnS4 absorbers and thin film solar cells prepared from dc-sputtered stacked metallic precursors. Three different time intervals, 10 min, 30 min and 60 min, at maximum sulphurization temperature were considered. The effects of this parameter' change were studied both on the absorber layer properties and on the final solar cell performance. The composition, structure, morphology and thicknesses of the CZTS layers were analysed. The electrical characterization of the absorber layer was carried out by measuring the transversal electrical resistance of the samples as a function of temperature. This study shows an increase of the conductivity activation energy from 10 meV to 54 meV for increasing sulphurization time from 10 min to 60 min. The solar cells were built with the following structure: SLG/Mo/CZTS/CdS/i-ZnO/ZnO:Al/Ni:Al grid. Several ac response equivalent circuit models were tested to fit impedance measurements. The best results were used to extract the device series and shunt resistances and capacitances. Absorber layer's electronic properties were also determined using the Mott-Schottky method. The results show a decrease of the average acceptor doping density and built-in voltage, from 2.0×10 17 cm −3 to 6.5×10 15 cm −3 and from 0.71 V to 0.51 V, respectively, with increasing sulphurization time. This results also show an increase of the depletion region width from approximately 90 nm to 250 nm.

Fabrication and characterization of kesterite Cu2ZnSnS4thin films deposited by electrostatic spray assisted vapour deposition method

“…The photovoltaic performance is comparable with recent published results of solar cell based on CZTS layer fabricated using non‐vacuum methods, e.g. .…”

Sodium doping effects on the crystalline and electrical properties of Cu2ZnSnSe4 thin films

“…The Na incorporation improved the crystallinity, purity and compositional uniformity of the CZTSe films so that the carrier concentration decreased obviously in MoB5, MoB10, and MoB30. However, MoB10 and MoB30 samples showed larger carrier concentration because of the excess Na incorporation (Li et al, 2013;Fernandes et al, 2013;Wätjen et al, 2012).…”

Anomalous persistent photoconductivity in Cu2ZnSnS4 thin films and solar cells

“…A typical Raman spectrum of the films is also shown in figure 1(d), where Lorentzian functions were used to deconvolute the spectrum into individual Raman peaks. The Raman spectrum is dominated by CZTS peaks, as well as the XRD pattern, although residual amounts of ZnS were also detected [33].…”